Electromagnetic relay with magnetic plastic hinge pad



June 6, 9 J. A. VASSALOTTI 3,32

ELECTROMAGNETIC RELAY WITH MAGNETIC-PLASTIC HINGE PAD Filed July 29,1965 I 'I I L I N VEN TOR. Julia/l Yassalafii BY ATTORNEY;

United States Patent 3,324,434 ELECTRQMAGNETIC RELAY WITH MAGNETICPLASTIC HINGE PAD John A. Vassalotti, Philadelphia, Pa., assignor toStruthers-Dnnn, Inc, Pittman, N.J., a corporation of Pennsylvania 7Filed July 29, 1965, Ser. No. 475,818 2 (Zlaims. Cl. 335-270) ABSTRACTOF THE DISCLOSURE An electromagnetic relay has a pad of yieldableplastic material between the frame and the armature at the pivot pointof the armature. The plastic pad contains finely divided magneticparticles.

This invention relates to an electrical relay capable of undergoingmillions of cycles of operation without failure due to wear.

Background and summary of the invention In pivoted armature structuresof the prior art, the repeated excursions of the armature has resultedin the development of wear particles which are liberated and, bymigrating to the contact area, ultimately tend to cause an open contact,resulting in failure of the relay. It is an object of this invention toovercome this disadvantage and to provide a relay having longer wear.

Relays of the prior art, utilizing electromagnets and metallic framesassociated with the flux path of the electromagnet, together with anarmature which is reciprocable back and forth about a pivot in the fluxpath, have been constructed in such a Way that an air gap is introducedin the flux path. This air gap requires an increased power input toproduce a given flux density, and the greater power input results in anincreased generation of heat thus increasing the temperature ofoperation of the relay.

It is, accordingly, another object of this invention to provide a relayhaving an excellent flux density but which is operable at a relativelylow power input and at a relatively low temperature. Other objects andadvantages of this invention, including the simplicity and economy ofthe same, and the ease with which it may be applied to relay structuresof various types, will further become apparent hereinafter and in thedrawings.

Brief description of the drawing FIG. 1 represents a view in sideelevation of a specific relay construction embodying features of thisinvention, with part of the cover shown broken away in order to revealimportant internal details;

FIGS. 2, 3 and 4 are sectional views taken as indicated by the lines andarrows IIII, III-III and IV-IV respectively, which appear in FIG. 1;

FIG. 5 is a view in perspective showing the pivot portion of thearmature appearing in the relay of the preceding figures;

FIG. 6 is a fragmentary view in prespective, and shown exploded,illustrating the parts that are associated with one another inconnection with the pivot structure;

FIG. 7 is a view in perspective showing pivot shoulders at the cornersof the armature;

FIG. 8 is an enlarged fragmentary view, shown in side elevation, of thepivot structure appearing in FIG. 1; and

FIG. 9 is an enlarged cross-sectional view of a preferred form ofmagnetic pad which is incorporated into the pivot structure.

3,324,434 Patented June 6, 1967 Description of the preferred embodimentTurning now to the specific form of the invention selected forillustration in the drawings, the relay shown in FIG. 1 has the usualsets of contacts 20 including spring elements 21 which normallyspring-urge an operating plate 22 upwardly away from an electromagnet 23also located within the housing 24. An armature 25 is mounted within aniron framework 26 for reciprocating rocking or pivoting movement aboutthat frame, in a manner further to be explained hereinafter. Theoperating member 22 is connected to the end of the armature 25 in suchmanner that it moves in conjunction with the end of said armature.

Electric means including a wire 30 is provided in order, selectively, toenergize and de-energize the electromagnet 23, thus alternatelyattracting the armature 25 downwardly toward the electromagnet, andreleasing the armature for movement upwardly under the influence of thespring-urged operating member 22. In this manner, the relay is caused toopen and close circuits passing through the switch contacts 20.

Having reference particularly to FIGS. 3-8 of the drawings, thestructure of the pivot as shown in the drawings will be apparent. Anupstanding member 35 of the frame 26 is screwed to another upstandingmember 36 having an outwardly directed flange 37. The armature 25 isprovided with downwardly coined corner sections 40 which contacts awater of yieldable plastic material 41, having novel features in thisinvention as will further be described. The armature is held in placewith respect to the upstanding member 35 by a spring clip 42 extendingunder a tongue 43 integral with the upstanding member 36.

The wafer 41, the preferred shape of which is shown most clearly in FIG.6 of the drawings, is preferably composed of thin vinyl plasticthoroughly impregnated with uniformly spaced finely divided particles offerrous metal, particularly magnetic iron oxide, all as shown in FIG. 9.This wafer has been found to have and to impart to the overall structurethe highly advantageous characteristics that have been referred toearlier in this specification.

It has been found that the presence of an air gap in the iron frameresults in high reluctance; thus; a thin air gap provides best resultsbut the more air gap is provided the more driving force is needed toproduce the same total flux. The fact that the vinyl wear pad is filledwith a multiplicity of spaced apart, finely divided particles ofmagnetic iron provides a reluctance factor which is approximatelysixteen times lower than that of air alone. This allows the provision ofa thicker vinyl gap between the metallic parts, giving better wearprotection but still not greatly increasing the driving force needed togenerate a given magnetic field. This is of considerable advantagesince, with a given voltage and circuit, a unit having the same drivingforce runs at a lower temperature, and uses less power to produce thesame contact actuating force.

Actually, this invention is so successful that as many as 42,000,000cycles have been performed in mechanical life tests, and the wear was onthe vinyl pad but not on the armature or on the hinge portions of theframe.

This invention is of particular advantage in connection with the wearproblem, since the structure is of low load, resulting in minimum vinyldistortion, since the pivot point is approximately at the end of thearmature, the spring force is approximately at the other end of thearmature, and the magnetic force acts downwardly at a locationintermediate the point of application of spring force and the locationof the pivot.

Although this invention has been disclosed in conjunction with aspecific form thereof, it will be understood that, subject to thelimitations expressed above, equivalent elements may be substituted forthose specifically disclosed, parts may be reversed, and certain partsmay be 3 used independently of others, all without departing from thespirit and scope of this invention as defined in the appended claims.

The following is claimed:

1. A relay comprising an alternating current electromagnet, a metallicframe positioned in the flux path of said electromagnet, a metallicarmature arranged across the frame and in the flux path, said armaturebeing swingably mounted upon a supporting portion of said frame formovement back and forth in response to energization and de-energizationof said electromagnet, and a piece of yieldable plastic materialdisposed between said frames and said armature at said supportingportion of said frame, said plastic material containing a multiplicityof spaced apart magnetic particles.

2. A relay comprising an electromagnet, a metallic frame associated withthe flux path of said electromagnet, a metallic armature arranged acrossthe frame and in the flux path, said armature being swingably mounted ata location near the end of said armature upon said frame pad of plasticmaterial containing a multiplicity of finely divided magnetic particlesdisposed between said frame and said armature at said supporting portionof said frame.

References Cited UNITED STATES PATENTS 2,275,924 3/1942 Seely 335-1282,973,464 2/1961 Wiberg 335-273 3,278,872 10/1966 Maynard 335128 XBERNARD A. GILHEANY, Primary Examiner.

G. HARRIS, JR., Assistant Examiner.

1. A RELAY COMPRISING AN ALTERNATING CURRENT ELECTROMAGNET, A METALLICFRAME POSITIONED IN THE FLUX PATH OF SAID ELECTROMAGNET, A METALLICARMATURE ARRANGED ACROSS THE FRAME AND IN THE FLUX PATH, SAID ARATUREBEING SWINGABLY MOUNTED UPON A SUPPORTING PORTION OF SAID FRAME FORMOVEMENT BACK AND FORTH IN RESPONSE TO ENERGIZATION AND DE-ENERGIZATIONOF SAID ELECTROMAGNET, AND A PIECE OF YIELDABLE PLASTIC MATERIALDISPOSED BETWEEN SAID FRAMES AND SAID ARMATURE AT SAID SUPPORTINGPORTION OF SAID FRAME, SAID PLASTIC MATERIAL CONTAINING A MULTIPLICITYOF SPACED APART MAGNETIC PARTICLES.